The use of radiofrequency (RF) generators and electrodes to be applied to tissue for pain relief or functional modification is well known. For example, the RFG-3C RF lesion generator of Radionics, Inc., Burlington, Mass. and its associated electrodes enable electrode placement of the electrode near target tissue and heating of the target tissue by RF power dissipation of the RF signal output in the target tissue. Temperature monitoring of the target tissue by a temperature sensor in the electrode can control the process. Heat lesions with target tissue temperatures of 60 to 95 degrees Celsius are common. Tissue dies by heating above about 45 degrees Celsius, so this process produces the RF heat lesion.
RF generators and electrodes are used to treat pain and other diseases. Examples are the equipment and applications of Radionics, Inc., Burlington, Mass. such as the RFG-3C RF lesion generator and the SMK electrode and other electrode systems. Related information is given in the paper by Cosman ER and Cosman BJ, “Methods of Making Nervous System Lesions”, in Wilkins RH, Rengachary S (eds.); Neurosurgery, New York, McGraw Hill, Vol. 3, 2490-2498; and is hereby incorporated by reference in its entirety.
The Radionics Pole Needle and RF Pole Needle have a shaft including a metal tubing with sharp distal end for insertion into tissue to reach a spinal target. The shaft of the RF pole needle is insulated except for an exposed conductive tip portion and has an electrical connection to a signal generator for delivery of stimulation or RF signal outputs to the target tissue. Each has a flexible injection tube and a port to allow injection of contrast, anesthetic, or saline solution fluid to the target tissue. Neither incorporates a built-in temperature sensor or adaptation to accept a temperature sensor. This has a disadvantage in RF lesion making because temperature monitoring of target tissue can be of significance to control the lesion process. Related information is given in Radionics brochures “Disposable RF cannula and RF electrodes, Pole Needles, and Injection Needles”, brochure number 700xxx, SMK-C/Pole N.-5/74-0, copyright 2987, Radionics, Inc., and is herby incorporated by reference herein in its entirety.
The Radionics SMK Kit includes an insulated cannula having a pointed metal shaft that is insulated except for an uninsulated electrode tip. The cannula has a hub at its proximal end having a luer fitting to accommodate a separate thermocouple (TC) electrode that can deliver electrical signal output such as RF voltage or stimulation to the uninsulated electrode tip. A disadvantage of this system is that fluid injection into the cannula cannot be achieved when the TC electrode is also in the cannula. Another disadvantage is that the temperature sensor probe and the cannula are separate elements, which increases the complexity of the components needed for the system. Related information is given in the Radionics brochure “Type SMK Sluijter-Mehta Kit”, number 700-1049-6-1991, copyright 1991, Radionics, Inc., and is hereby incorporated by reference in its entirety.
The Neurotherm Disposable Stimject kit includes a cannula that is insulated except for an exposed conductive tip. The cannula has a hub with a luer fitting. The Stimject kit has a “Tconnector” which is separate from the cannula and is connected to the luer fitting of the cannula after the cannula is inserted into the living body of the patient. The Tconnector has a flexible side port including flexible tubing that enters the side of the Tconnector. The tubing has on its end, a luer fitting that can accept a TC electrode. The TC electrode is separate from the Tconnector and the cannula, and comes as part of the Stimject kit. Once the cannula, Tconnector, and TC electrode are locked together, then injection, stimulation, and RF signal output can be applied without further connection to the cannula. One disadvantage is that the cannula, the injection port element (the Tconnector), and the TC electrode are all separate elements that must be connected together during the procedure and after the cannula is placed in the patient. This increases complexity, manipulations, and time of the procedure. Manipulations can cause movement of the cannula once it is properly placed at the target tissue, which has the disadvantage of losing accuracy of the procedure. Related information is given in the RDG Medical brochure “NeuroTherm Disposable Stimject Kit”, brochure number RF104, 2004; and is hereby incorporated by reference herein in its entirety.
The LCE-TC, KCTE-TC, and TCE-TC electrodes of Radionics, Inc. are designed for making RF heat lesions in the spinal cord. They have very small diameter metal tubing shafts and uninsulated electrode tips, which is required for cordotomy application since the target tissue inside the spinal cord is very small and critical. The LCE-TC and KTCE-TC electrodes have shaft diameters of approximately 0.3 mm corresponding to 0.013″ and 29 gauge stainless steel tubing shafts. A pointed tip at the distal end of the uninsulated electrode tip is in the shape of a conical point formed by welding shut the metal tubing of the shaft. The TCE-TC electrodes have shaft diameter of 0.5 mm, corresponding to 0.020″ and 25 gauge stainless steel tubing shaft. A pointed tip at the distal end of the uninsulated electrode tip is in the shape of a conical point formed by welding shut the metal tubing of the shaft. Built into the tip of these electrodes is a thermocouple temperature sensor. The Radionics prospectuses on these electrodes are hereby incorporated by reference in its entirety. The LCE-TC and KTCE-TC electrodes have an integrally connected, non-separable, flexible electrical connection at its hub (or proximal) shaft end that enables connection to a RF generator. The TCE-TC electrode has a connection for the high frequency and the temperature sensor connection is inseparably built into its hub. The electrodes are very thin and flexible and are used to for RF heat lesion making in tiny target tissues in the spinal cord. One disadvantage is that these electrodes require an ancillary guidance needle or cannula to enable initial penetration of the skin and guidance through tissues of the neck. These electrodes have another disadvantage in that they require a separate depth stop to verniate their depth of penetration. Another disadvantage that these electrodes require multiple, separate parts to be used, which increases the complexity of the equipment and the cost to build it. Another disadvantage is that the metal tubing shafts with diameters of 0.3 to 0.5 mm are too flexible and delicate for self-supported penetration of skin and tissue on the way towards a nerve target near the spinal cord or spinal nerves. A further disadvantage is that the uninsulated electrode tip diameters of about 0.3 to 0.5 millimeters are also too small to make adequate-sized heat lesions in the spinal nerves and ganglia in many clinical situations. The electrodes also have another disadvantage in that their conical shaped pointed tips are not optimal for penetration of tough tissue on the way into the region the spinal facet joints and dorsal root ganglion. The electrodes also have no capability of injecting fluid directly through them, which is useful in some clinical situations.
The Cool-Tip Electrode of Radionics and Valley Lab, Inc. is a 16-gauge (or 1.6 millimeter diameter) electrode with partially insulated shaft and water-cooling channel inside its rigid cannula shaft. The brochure from Radionics is hereby incorporated by reference in its entirety. The Cool-Tip Electrode is used specifically for making very large RF heat ablations of cancerous tumors, primarily in soft-tissue organs. It has a closed trocar point that includes a metal plug that is welded to the metal tubing that is part of the electrode shaft. The distal end of the metal plug is sharpened to form a three sided, axially symmetric trocar. The distal end is a closed and sealed metal structure. The sharpened portion of the distal tip does not include the metal tubing itself, but rather the sharpened end of the metal plug that is welded to the metal tubing. This has a disadvantage in that it is a more complex construction involving multiple substructures and multiple construction operations such as welding the trocar point to the metal shaft. The temperature sensor is built into the electrode distal tip, and it is configured to measure the temperature of cooling fluid in the inner space of the metal tubing of the electrode shaft. This has a disadvantage that the temperature sensor has reduced speed and accuracy in measuring tissue temperature immediately outside the uninsulated electrode tip. Another disadvantage is that the temperature sensor can not be visualized from the outside because of the closed metal tip which makes it more difficult to determine its location inside the uninsulated electrode tip. The electrode has flexible RF electrical connection and flexible thermocouple wire connections that are connected to the proximal hub of the electrode shaft. The electrode has no adaptation for fluid injections through its shaft and into the target tissue. The 16-gauge cannula has too large a diameter for general use for RF applications on spinal nerves and ganglia, especially in the cervical region or near dorsal root ganglia. The thermocouple sensor in the Cool-Tip electrode is also located in the cooling fluid channel inside the distal end, and is not in close mechanical and thermal contact with the outer metal tubing of the uninsulated electrode tip, exposed electrode tip or to the surface of the exposed electrode tip. This has the disadvantage in that temperature measurement of tissue temperatures near the tip can be slow responding and inaccurate. Such a disadvantage can be inadequate for RF applications at spinal nerves or ganglia.
The RRE Electrode of Radionics, Inc. has a 16 gauge metal tubing shaft that is insulated except for an uninsulated electrode tip that has a trocar distal point. It has a shaft and an integrally attached hub. The Radionics prospectus on the RRE electrode is hereby incorporated by reference in its entirety. The RRE electrode shaft includes a 16 gauge metal tubing. Its symmetrical three-sided trocar tip is formed by welding onto the metal tubing a stainless steel plug that is than ground to have a trocar pointed tip end. It has a unitized construction with closed metal tip. This has one disadvantage in that the position of the temperature sensor inside the electrode cannot be visualized checked from the outside during or after assembly. The RRE electrode has a closed trocar point that includes a metal plug that is welded to the metal tubing that is part of the electrode shaft. The distal end of the metal plug is sharpened to form a three sided, axially symmetric trocar. The distal end is a closed and sealed metal structure. The sharpened portion of the distal tip does not include the metal tubing itself, but rather the sharpened end of the metal plug that is welded to the metal tubing. This has a disadvantage in that it is a complex construction involving multiple substructures and multiple construction operations such as welding the trocar point to the metal shaft. The tip and shaft are in a straight-line geometry. This has one disadvantage, compared to a curved-tip electrode, in that the electrode cannot be steered as easily as a curved-tip shaft, and its tip can not be contoured or curved next to a curved nerve path as is often convenient for the facet nerve treatments. The RRE electrode has a temperature sensor inside the metal tubing at the distal tip and near the welded on stainless steel plug that is part of the trocar point. The temperature sensor is not at the external surface of the electrode distal tip. This has one disadvantage in that the temperature readings are not made immediately in contact with the target tissue that is being treated during a high frequency therapy, which can degrade the effectiveness of the procedure. Another disadvantage is that because the temperature sensor is not close to the very tip and surface of the uninsulated electrode tip, the temperature measurements can be slow and inaccurate. Another disadvantage is that the position of the temperature sensor with respect to the metal tubing and the metal trocar plug cannot be seen externally, and thus cannot be visually inspected from the outside. This has the disadvantage that the temperature sensor may not be in close thermal contact with the tubing wall or the trocar tip, which reduces the speed of response and the accuracy of the temperature readings. Another disadvantage is that the position of the temperature sensor, which is important for the accuracy of temperature measurement, cannot be easily checked during or after electrode assembly. Because of the thickness of the metal tubing and the trocar tip, the electrode tip structure has a significant thermal mass, and the temperature sensor is not in close thermal contact with the outer wall of the tubing. This has a disadvantage that its thermal response to temperature changes in the tissue immediately outside the RF tip is slow. Another disadvantage is that the RRE electrode construction is complex, expensive, and does not lend itself to full inspection of it internal structure. The RRE electrode does not have flexible electrical connections for the high frequency signal or the temperature sensor signal. This has a disadvantage that, once the electrode is placed at the target in the patient body, any connection of wires to the high frequency generator can disturb the proper electrode position, causing inaccuracies is the clinical procedure. The RRE electrode does not have a radio opaque material of significantly different radio opacity form the stainless steel of the tubing and the trocar point. This has a disadvantage that a clear discrimination of the position of the electrode tip under x-ray control can be made difficult or unclear.
The TCE-TC and the stereotactic electrodes of Radionics, Inc. have unitized construction of a metal tubing shaft, a hub with non-flexible electrical connections for temperature sensing and high frequency generator signal outputs, and closed metal construction of their uninsulated electrode tip. The Radionics prospectuses are hereby incorporated by reference in their entirety. The stereotactic electrodes have typically rounded tip ends. This has one disadvantage that they are not appropriate for self-penetration of skin and tissue around the spine. The TCE-TC electrode has a 0.5 mm shaft diameter and a conically pointed distal tip. It is designed to be carried inside a guide needle of 1.3 mm outer diameter. The guide needle is used to first penetrate the skin and tissue of the neck before the TCE-TC electrode is inserted through the guide needle. The point of the TCE electrode is used only to pierce and penetrate the spinal cord in the final step of a cordotomy pain procedure. The TCE electrode by itself is too thin and flexible to be used to self-penetrate skin, musculature, and other connective tissue of the spinal region, which is involved in performing percutaneous facet denervations and dorsal root ganglion procedures.